Coming from the 6H30Pi (EH, so *theoretically* just a tad better than the Sovtek), the 6H30P-DR brought a truly holographic (3D) soundstage; that was the first immediately obvious improvement, even before burn-in. After burn-in, much better extension, especially in the bass department (200Hz downwards), flying detailed highs and great transients, and a naturalness of timbres and decay that I had not heard before. Not minute differences, but quite major, and that was before I upgraded a few more pieces of gear like my S/PDIF transport and battery power, which made another night and day difference that scaled extremely well with the -DR and CV4015, even moreso with the HE-500 and good CV4014 tubes with more power and thump.

I'll try my 6H30Pi again this week, just out of curiosity when I change my power tubes before shipping them. Just to anti-placebo myself again. I ought to sell my 6H30Pi too, it seems useless to keep them for no reason when they're definitely worth something and close to new...

Thanks for posting your impressions. Appreciated. Interesting, because the negatives of the 6H30P-EV, I found, were a relatively flat stage, the other the lacking sub bass, both seem to be improved with the DRs.

I have heard that battery give cleaner power. What setup do you use and do you use it for DAC and LD?

Thanks for posting your impressions. Appreciated. Interesting, because the negatives of the 6H30P-EV, I found, were a relatively flat stage, the other the lacking sub bass, both seem to be improved with the DRs.

I have heard that battery give cleaner power. What setup do you use and do you use it for DAC and LD?

Check the Hiface Two thread in computer audio for more details, the two last pages. Basically I use a M2Tech Hiface Two and a Little Dot DAC_1 (with AD797BR opamps (now RoHS compliant -BRZ) instead of the stock LM4562, which make are some of the best opamps you can get, and rival with discrete solutions) connected to my LD MK IV SE.

The DAC_1 is a very nice unit with a single Wolfson WM8740 DAC chip (compared to 2 in the Cambridge Audio Dac Magic) and a toroidal transformer (unlike the Dac Magic). I'm still surprised how well it still scales with every gear upgrade I've made over the last year (like the MK IV SE, I have not found its limit yet, which is surprising for $300-$400 gear). But its USB input is just decent like most mid-fi DACs. Which is why I use the Hiface 2.

The Hiface 2 uses "so-called" crappy USB 5V power (didn't believe in this until I changed its power supply) to power its onboard converters and clocks. Like for most USB-S/PDIF converters, there are many reports of massive changes in sound quality with better power supplies and batteries, but at a very high cost (like the John Kenny JKSPDIF & JKDAC both based on the Hiface with LieFePo4 batteries).

So, I first made a DIY 5V USB power injector powered by an old phone charger, just to try it out, and found an immense improvement. I then made another USB hijack 5V power injector with a USB male adapter and a "5V" USB battery pack with a female USB plug, which I filled with 4 rechargeable Ni-MH batteries to get a clean 5V off-grid power supply lasting 15-20h. For the first time, I think I got close to hearing sounds from heaven on my HE-500, the difference was that dramatic, seriously. Don't believe me, try it for yourself. the weakest link in a computer-based audio system is the software and S/PDIF transport (or lack thereof if you can manage to get/make an I2s-based battery-powered USB transport-DAC, which I'll eventually lean towards when I have the cash). The two main limiting factors in my, at this point fairly optimized system, are the computer and S/PDIF stages and of course the tubes in my head amp, connected directly to my headphones (OTL design), hence my participating in this thread.

Out of curiosity, what USB-S/PDIF (or other digital) interface/transports do all you people use here with you LD amps (if you have one)?

Check the Hiface Two thread in computer audio for more details, the two last pages. Basically I use a M2Tech Hiface Two and a Little Dot DAC_1 (with AD797BR opamps (now RoHS compliant -BRZ) instead of the stock LM4562, which make are some of the best opamps you can get, and rival with discrete solutions) connected to my LD MK IV SE.

The DAC_1 is a very nice unit with a single Wolfson WM8740 DAC chip (compared to 2 in the Cambridge Audio Dac Magic) and a toroidal transformer (unlike the Dac Magic). I'm still surprised how well it still scales with every gear upgrade I've made over the last year (like the MK IV SE, I have not found its limit yet, which is surprising for $300-$400 gear). But its USB input is just decent like most mid-fi DACs. Which is why I use the Hiface 2.

The Hiface 2 uses "so-called" crappy USB 5V power (didn't believe in this until I changed its power supply) to power its onboard converters and clocks. Like for most USB-S/PDIF converters, there are many reports of massive changes in sound quality with better power supplies and batteries, but at a very high cost (like the John Kenny JKSPDIF & JKDAC both based on the Hiface with LieFePo4 batteries).

So, I first made a DIY 5V USB power injector powered by an old phone charger, just to try it out, and found an immense improvement. I then made another USB hijack 5V power injector with a USB male adapter and a "5V" USB battery pack with a female USB plug, which I filled with 4 rechargeable Ni-MH batteries to get a clean 5V off-grid power supply lasting 15-20h. For the first time, I think I got close to hearing sounds from heaven on my HE-500, the difference was that dramatic, seriously. Don't believe me, try it for yourself. the weakest link in a computer-based audio system is the software and S/PDIF transport (or lack thereof if you can manage to get/make an I2s-based battery-powered USB transport-DAC, which I'll eventually lean towards when I have the cash). The two main limiting factors in my, at this point fairly optimized system, are the computer and S/PDIF stages and of course the tubes in my head amp, connected directly to my headphones (OTL design), hence my participating in this thread.

Out of curiosity, what USB-S/PDIF (or other digital) interface/transports do all you people use here with you LD amps (if you have one)

I use my asus essence stx soundcard as dac for my Littledot MK3 with a pair of Denon LA D-5000 it sounds good for a $200.00 amp but i also use a Burson 160ds that sounds very good. With hi res files you dont want to go back to listening 44.1 files, thats like tube rolling,you get sucked in, takes up a lot of space dough.

Another thing I'm curious about is the gain setting I should be using. My Senns are 64ohm and I've got the gain set to 5. I didn't think that 64ohm headphones would be considered "low impedance".

64 ohms, while not low impedance per se, is still pretty low. Depending on your headphone sensitivity, I'd use either gain 5 or 10. I find my amp sounds better on 10 regardless of headphones, with more apparent power reserve.

An interesting piece of information I just found browsing google for ideas, as one might on a Sunday afternoon. I'd been wondering which suffix letters on Russian tubes mean long life, which ones ruggedized and so on. Here's what I found :

"There are suffixes to the Russian valve numbers which indicate certain things -
E (same in cyrillic)indicates a ruggedised construction.
V (B in cyrillic) indicates military use - often means they draw a little more heater current than usual to get a lower noise figure.
I (a backwards N in cyrillic) indicates that a valve is intended for pulse mode operation - these valves usually have a shorter working life, but can stand higher B+ than the standard designs.
R (P in cyrillic) indicates low noise spec..
D (a squiggly A with the top crossed over in cyrillic) means a 10K hour valve, automatically implies rugged construction - a European SQ type."

So, again that explains the short life of 6N6P-I, as I think Mordy reminded us of a few pages back. But it would also imply that 6N6P-IR are basically the same thing with better noise specs, and in no way a longer life, or a normal life for that matter... Seems important enough to point out, as these still cost a few dozen dollars a pair, getting closer to the price of 6H30P. It also explains why all the -DR tubes (there aren't many types with DR suffixes actually) also sound great apart from having long lifetimes.

Now, this has got me wondering if I made the right call buying 6J3P-E, and if I shouldn't have waited for an even higher spec model to pop up...

An interesting piece of information I just found browsing google for ideas, as one might on a Sunday afternoon. I'd been wondering which suffix letters on Russian tubes mean long life, which ones ruggedized and so on. Here's what I found :

"There are suffixes to the Russian valve numbers which indicate certain things -
E (same in cyrillic)indicates a ruggedised construction.
V (B in cyrillic) indicates military use - often means they draw a little more heater current than usual to get a lower noise figure.
I (a backwards N in cyrillic) indicates that a valve is intended for pulse mode operation - these valves usually have a shorter working life, but can stand higher B+ than the standard designs.
R (P in cyrillic) indicates low noise spec..
D (a squiggly A with the top crossed over in cyrillic) means a 10K hour valve, automatically implies rugged construction - a European SQ type."

So, again that explains the short life of 6N6P-I, as I think Mordy reminded us of a few pages back. But it would also imply that 6N6P-IR are basically the same thing with better noise specs, and in no way a longer life, or a normal life for that matter... Seems important enough to point out, as these still cost a few dozen dollars a pair, getting closer to the price of 6H30P. It also explains why all the -DR tubes (there aren't many types with DR suffixes actually) also sound great apart from having long lifetimes.

Now, this has got me wondering if I made the right call buying 6J3P-E, and if I shouldn't have waited for an even higher spec model to pop up...

Out of curiosity, what USB-S/PDIF (or other digital) interface/transports do all you people use here with you LD amps (if you have one)?

Thank you for the details Audiofanboy. I suppose that most commonly people use a DAC as their USB/SPDIF interface. I have been using a Beresford Caiman and recently bought an Audiolab M-DAC. The sound signatures are quite different. Please ask me for more details if you are interested.

As a SS-option I am running an SPL Auditor, which has a unique 120 V technique to prevent distortion and over-driving chips, also it sounds neutral and has non-fatiguing treble.

Yes, it seems there are conflicting information on the web for 6N6P-IR and thanks for sharing the details! But I am not worried about a shorter lifetime, even 500 h means probably a year of listening, and if they are better and extend to 2 to 3 years, that's enough for me. I wouldn't mind buying a pair every 3 years and god knows what amp I might have in 10 years... Additionally, there is no other tube that gives me the sound signature the IR provides, and as it stands, only the quite pricey 6H30P-DR would be an upgrade for me, of - at the moment - unknown quantity. So, I just enjoy the sound and see what happens.

And thanks Mikelap for posting this informative an comprehensive pic, only letter I am missing is the R (Russian P) as an ending descriptor, which Audiofanboy has picked up as low noise spec.

Thank you for the details Audiofanboy. I suppose that most commonly people use a DAC as their USB/SPDIF interface. I have been using a Beresford Caiman and recently bought an Audiolab M-DAC. The sound signatures are quite different. Please ask me for more details if you are interested.

As a SS-option I am running an SPL Auditor, which has a unique 120 V technique to prevent distortion and over-driving chips, also it sounds neutral and has non-fatiguing treble.

Yes, it seems there are conflicting information on the web for 6N6P-IR and thanks for sharing the details! But I am not worried about a shorter lifetime, even 500 h means probably a year of listening, and if they are better and extend to 2 to 3 years, that's enough for me. I wouldn't mind buying a pair every 3 years and god knows what amp I might have in 10 years... Additionally, there is no other tube that gives me the sound signature the IR provides, and as it stands, only the quite pricey 6H30P-DR would be an upgrade for me, of - at the moment - unknown quantity. So, I just enjoy the sound and see what happens.

And thanks Mikelap for posting this informative an comprehensive pic, only letter I am missing is the R (Russian P) as an ending descriptor, which Audiofanboy has picked up as low noise spec.

So you use an oversampling DAC, I hear that doesn't always mix well with USB-Digital interfaces (DAC oversamples to reduce the effects of jitter as it is, so further optimizations may not help much); I guess we use different strategies, hopefully with similar good results!

Speaking of SS and extra power, I finally managed to find out whether the output power specs of the LD amps are for both channels or for each. Good news: it's for each. So, that's a minimum of 200 mW total @ 32 ohms, hopefully a bit more at for orthos with a slightly higher impedance rating and with higher current draw tubes. Maybe something like 300 mW total in practice on a HE-500 (far from the recommended 1W, but getting closer as things get optimized).

About the 6N6P-IR, I just figured it might be a useful piece of information before splurging and buying a huge stash of them (or to go ahead and buy a stash of them just in case they don't last that long, either way lol).

After -E, -EV/EB, -I, -IR, -DR, I've discovered there are also -ER Russian tubes (long life / high reliability, low noise like all the best power tubes we like).

I just got three different types of tubes in the mail today, the first of a loooong list I intend to investigate. Mullard CV5377 from 1968 (special quality CV4014, which were special quality 6AM6, which are sp... You get the point), Canadian GE 6676 made by US GE 6CB6A/6676 (NOS, so burn-in required before any serious listening), and GE 8136 (instrument version of the 6DK6) used so I should report back about these soon.

"Oversampling is the process by which an analog signal is digitally sampled well above the Nyquist rate (2x it's real bandwidth). Upsampling is a process by which an already digitally sampled signal is sampled above it's original sampling rate."

In summary, upsampling seems not good for the signal, whereas oversampling is quite common and generally found to be useful. But, yes it does basically "interpolate" steps in the original signal curve. I am not sure what the context with jitter is. Oversampling is much older than the knowledge about jitter, think about the old and glorious Philips 4 x oversampling chips. There is a de-jittering mechanism in place for the M-DAC but to be fair I haven't yet researched how it works.

LD power

Excellent! I think if we manage 400 mW that would be a useful (surely not optimal, but still) amount of power. I heave read that - in theory - 6H30 tubes for example can do 4 W max, as well as 300 V, if the environment supports it. Now, I have to check on the 6N6P tubes, but even if it is just 1 W, and maybe even 500 mW in the context of the LD, then that's a reasonable to good value for the HE-500. Another question is whether the higher gain also relates to more effective power or just more loudness. I have read about this before. Usually, louder sounds better though it seems.

6N6P-IR

Yeah, it was an interesting finding. I would still wholeheartedly recommend to get one pair and then see for yourself :)